1. Field of the Invention
The present invention generally relates to switches for electronic and electrical apparatus and, more particularly, to miniature switches which are suitable for retrofitting electrical and electronic apparatus to other devices and controlling the electrical or electronic apparatus in conjunction therewith.
2. Description of the Prior Art
Control must be exercised over virtually all electronic or electrical apparatus in order to derive desired functions therefrom. To exercise such control, some device must provide an interface between the apparatus and some external agency such as a condition sensor or, much more often, a human operator. It is sometimes the case that control of a device will be desired in conjunction with operation or control of some other apparatus or system with which the device otherwise cooperates only minimally, if at all. In such a case, either operation or the control of the other apparatus or system must be sensed and converted to an electrical signal suitable for exercising the desired control of the device.
For example, it is known to sense current in one circuit and to control application of power to the another circuit. Thus, as applied in a commercially available power strip to an installation of a personal computer or audio system, the usually accessible power connection to, say, the monitor or the printer of a personal computer or the pre-amplifier, tuner or other component of an audio system, may be used to remotely control application of power to other components of the system where the individual switches therefor are not necessarily accessible or where the convenience of a single power switch for all system components is desired.
In other arrangements which involve separated but similar power sources such as in multi-pole circuit breakers or switches, a simple mechanical interlock between similar switch structures may be sufficient to commonly control separate circuits. In contrast, complex proximity sensing circuits (e.g. capacitive or radiant energy sensors) or signals representing changes in any of a number of different control functions of a device may be used in conjunction with knobs or keypads to provide an additional control function for the same or another device. For example, in some consumer electronics devices such as a car radio, adjustment of any control (e.g. volume) will cause temporary display of alternative data (e.g. tuner frequency rather than time) on a display. However, unless some structural or functional similarity or cooperation can be exploited, auxiliary switching or sensor arrangements are generally bulky, complicated, expensive and/or difficult to retrofit to existing apparatus or systems.
It has recently been proposed to provide a voice recording device in an electrical wall switch plate, such as is disclosed and claimed in co-pending U.S. patent application Ser. No. 08/685,609, filed Jul. 24, 1996 (now abandoned), of which the present inventor is a joint inventor and which application is hereby fully incorporated by reference as if the text thereof were fully set forth herein. In this combination, it is contemplated that the actuation of the wall switch should cause the playback of an audio message of one or more messages (possibly of a sequence of messages) that may be recorded at will, preferably by recording samples of the message in random access memory or other solid state memories.
Such recordation has been facilitated by recent reductions in cost of relatively large capacity semiconductor memories and integrated circuits capable of conversion of analog signals to digital signals and vice-versa. Thus, it is possible to provide the necessary electronics, including a speaker, microphone and battery power supply within a wall switch plate cover with only a relatively modest increase in the thickness thereof (e.g. about a 7/16 inch overall thickness, increasing thickness over a conventional switch plate generally by less than 1/4 inch).
Incidentally, at the current state of design of this device, it is preferred to activate the playback function by a brief signal pulse with automatic reset of the playback circuit when the message playback is complete. Thus the preferred function of sensing actuation of the wall switch differs widely from the function of the wall switch itself or the circuit to which it is connected. Further, it is considered desirable to be able to distinguish between directions of actuation to provide different messages for each wall switch state or to control a sequence of messages. Sensing of circuit conditions may also be complicated by so-called three-way or four-way switch connections which may allow a circuit to be controlled from multiple locations potentially remote from the playback device.
However, providing sensing of operation of a wall switch as desired for this application within a switch plate cover is not trivial. The existing wall switch provides the mounting arrangement for the switch plate and conventional switch plates are designed to be drawn tightly against the body of the wall switch with virtually the entirety of the actuating lever of the wall switch protruding therethrough. Of course, external mechanisms would be unsightly and potentially dangerous.
Current sensing in the controlled circuit is less than fully reliable due to possible variation or disconnection of the load controlled by the switch and, in any event, it is desirable for purposes of simplicity and safety of installation of the device to retrofit it to an existing wiring system without disturbance of existing wiring in any way. Prevailing electrical codes may prohibit and restrict any incursion of any portion of the device or its circuitry into an existing electrical wiring box.
The need for linking of a switch or other structure to an existing electrical switch within a small volume is not limited to the device disclosed in the above-incorporated application. While many arrangements for operationally linking switches and electrical circuits are known, none are suitable for providing sensing of actuation and/or direction of actuation within a small thickness and within a wall switch cover plate with only a marginal increase in thickness thereof. Further, the required thinness of a switch may limit its ability to withstand thousands of actuations of the switch to which is to be connected.